Search for the candidate gene of a novel polyglutamine disease using proteomics.

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We have found three novel polyglutamine (polyQ) disease families in last four years. In histological examination of the nervous system, each case has shown unique distribution of the polyQpositive neuronal nuclei. We revealed one case was a homozygote of SCA17, and reported the clinico-pathological findings.After informed consent, we analyzed the protein extracted from autopsied brain. We found a case had an extra band in western blotting pattern using antibody to polyQ stretches (1C2).To profile the expression of proteins, we used 2D fluorescence difference gel electrophoresis (2D-DIGE) system (Amersham Bioscience). We chose a patient, who had been revealed as novel polyQ disease, and six controls. The protein samples were extracted from their cerebellum, and were labeled with CyDyes (patient : Cy5, control : Cy3, and internal standard : Cy2). The samples were separated over first and second dimensions according to their charge and size, respectively. Once the samples had been separated in the second dimension, gels were scanned for Cy2, Cy3 and Cy5 fluorescence using an appropriate scanner, Typhoon TM 9400 imager (Amersham Bioscience). And image analysis was performed using DeCyder (Amersham Bioscience). As a result, we discovered a certain protein which was expressed massively in the patient's brain. Besides, from the result of 2D western blotting, the protein was the very thing that we have recognized as an extra band in the 1D western blotting with 1C2. We picked the protein spot, and sequenced the peptide fragments by MALDI-TOF mass spectrometry. We could not find the candidate gene, however, we could build up the systems to find abnormal proteins quickly.